xref: /openbmc/linux/crypto/lrw.c (revision dbf4d133)
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* LRW: as defined by Cyril Guyot in
3  *	http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
4  *
5  * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
6  *
7  * Based on ecb.c
8  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
9  */
10 /* This implementation is checked against the test vectors in the above
11  * document and by a test vector provided by Ken Buchanan at
12  * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
13  *
14  * The test vectors are included in the testing module tcrypt.[ch] */
15 
16 #include <crypto/internal/skcipher.h>
17 #include <crypto/scatterwalk.h>
18 #include <linux/err.h>
19 #include <linux/init.h>
20 #include <linux/kernel.h>
21 #include <linux/module.h>
22 #include <linux/scatterlist.h>
23 #include <linux/slab.h>
24 
25 #include <crypto/b128ops.h>
26 #include <crypto/gf128mul.h>
27 
28 #define LRW_BLOCK_SIZE 16
29 
30 struct priv {
31 	struct crypto_skcipher *child;
32 
33 	/*
34 	 * optimizes multiplying a random (non incrementing, as at the
35 	 * start of a new sector) value with key2, we could also have
36 	 * used 4k optimization tables or no optimization at all. In the
37 	 * latter case we would have to store key2 here
38 	 */
39 	struct gf128mul_64k *table;
40 
41 	/*
42 	 * stores:
43 	 *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
44 	 *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
45 	 *  key2*{ 0,0,...1,1,1,1,1 }, etc
46 	 * needed for optimized multiplication of incrementing values
47 	 * with key2
48 	 */
49 	be128 mulinc[128];
50 };
51 
52 struct rctx {
53 	be128 t;
54 	struct skcipher_request subreq;
55 };
56 
57 static inline void setbit128_bbe(void *b, int bit)
58 {
59 	__set_bit(bit ^ (0x80 -
60 #ifdef __BIG_ENDIAN
61 			 BITS_PER_LONG
62 #else
63 			 BITS_PER_BYTE
64 #endif
65 			), b);
66 }
67 
68 static int setkey(struct crypto_skcipher *parent, const u8 *key,
69 		  unsigned int keylen)
70 {
71 	struct priv *ctx = crypto_skcipher_ctx(parent);
72 	struct crypto_skcipher *child = ctx->child;
73 	int err, bsize = LRW_BLOCK_SIZE;
74 	const u8 *tweak = key + keylen - bsize;
75 	be128 tmp = { 0 };
76 	int i;
77 
78 	crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
79 	crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
80 					 CRYPTO_TFM_REQ_MASK);
81 	err = crypto_skcipher_setkey(child, key, keylen - bsize);
82 	if (err)
83 		return err;
84 
85 	if (ctx->table)
86 		gf128mul_free_64k(ctx->table);
87 
88 	/* initialize multiplication table for Key2 */
89 	ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
90 	if (!ctx->table)
91 		return -ENOMEM;
92 
93 	/* initialize optimization table */
94 	for (i = 0; i < 128; i++) {
95 		setbit128_bbe(&tmp, i);
96 		ctx->mulinc[i] = tmp;
97 		gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
98 	}
99 
100 	return 0;
101 }
102 
103 /*
104  * Returns the number of trailing '1' bits in the words of the counter, which is
105  * represented by 4 32-bit words, arranged from least to most significant.
106  * At the same time, increments the counter by one.
107  *
108  * For example:
109  *
110  * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
111  * int i = next_index(&counter);
112  * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
113  */
114 static int next_index(u32 *counter)
115 {
116 	int i, res = 0;
117 
118 	for (i = 0; i < 4; i++) {
119 		if (counter[i] + 1 != 0)
120 			return res + ffz(counter[i]++);
121 
122 		counter[i] = 0;
123 		res += 32;
124 	}
125 
126 	/*
127 	 * If we get here, then x == 128 and we are incrementing the counter
128 	 * from all ones to all zeros. This means we must return index 127, i.e.
129 	 * the one corresponding to key2*{ 1,...,1 }.
130 	 */
131 	return 127;
132 }
133 
134 /*
135  * We compute the tweak masks twice (both before and after the ECB encryption or
136  * decryption) to avoid having to allocate a temporary buffer and/or make
137  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
138  * just doing the next_index() calls again.
139  */
140 static int xor_tweak(struct skcipher_request *req, bool second_pass)
141 {
142 	const int bs = LRW_BLOCK_SIZE;
143 	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
144 	struct priv *ctx = crypto_skcipher_ctx(tfm);
145 	struct rctx *rctx = skcipher_request_ctx(req);
146 	be128 t = rctx->t;
147 	struct skcipher_walk w;
148 	__be32 *iv;
149 	u32 counter[4];
150 	int err;
151 
152 	if (second_pass) {
153 		req = &rctx->subreq;
154 		/* set to our TFM to enforce correct alignment: */
155 		skcipher_request_set_tfm(req, tfm);
156 	}
157 
158 	err = skcipher_walk_virt(&w, req, false);
159 	if (err)
160 		return err;
161 
162 	iv = (__be32 *)w.iv;
163 	counter[0] = be32_to_cpu(iv[3]);
164 	counter[1] = be32_to_cpu(iv[2]);
165 	counter[2] = be32_to_cpu(iv[1]);
166 	counter[3] = be32_to_cpu(iv[0]);
167 
168 	while (w.nbytes) {
169 		unsigned int avail = w.nbytes;
170 		be128 *wsrc;
171 		be128 *wdst;
172 
173 		wsrc = w.src.virt.addr;
174 		wdst = w.dst.virt.addr;
175 
176 		do {
177 			be128_xor(wdst++, &t, wsrc++);
178 
179 			/* T <- I*Key2, using the optimization
180 			 * discussed in the specification */
181 			be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
182 		} while ((avail -= bs) >= bs);
183 
184 		if (second_pass && w.nbytes == w.total) {
185 			iv[0] = cpu_to_be32(counter[3]);
186 			iv[1] = cpu_to_be32(counter[2]);
187 			iv[2] = cpu_to_be32(counter[1]);
188 			iv[3] = cpu_to_be32(counter[0]);
189 		}
190 
191 		err = skcipher_walk_done(&w, avail);
192 	}
193 
194 	return err;
195 }
196 
197 static int xor_tweak_pre(struct skcipher_request *req)
198 {
199 	return xor_tweak(req, false);
200 }
201 
202 static int xor_tweak_post(struct skcipher_request *req)
203 {
204 	return xor_tweak(req, true);
205 }
206 
207 static void crypt_done(struct crypto_async_request *areq, int err)
208 {
209 	struct skcipher_request *req = areq->data;
210 
211 	if (!err) {
212 		struct rctx *rctx = skcipher_request_ctx(req);
213 
214 		rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
215 		err = xor_tweak_post(req);
216 	}
217 
218 	skcipher_request_complete(req, err);
219 }
220 
221 static void init_crypt(struct skcipher_request *req)
222 {
223 	struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
224 	struct rctx *rctx = skcipher_request_ctx(req);
225 	struct skcipher_request *subreq = &rctx->subreq;
226 
227 	skcipher_request_set_tfm(subreq, ctx->child);
228 	skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
229 	/* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
230 	skcipher_request_set_crypt(subreq, req->dst, req->dst,
231 				   req->cryptlen, req->iv);
232 
233 	/* calculate first value of T */
234 	memcpy(&rctx->t, req->iv, sizeof(rctx->t));
235 
236 	/* T <- I*Key2 */
237 	gf128mul_64k_bbe(&rctx->t, ctx->table);
238 }
239 
240 static int encrypt(struct skcipher_request *req)
241 {
242 	struct rctx *rctx = skcipher_request_ctx(req);
243 	struct skcipher_request *subreq = &rctx->subreq;
244 
245 	init_crypt(req);
246 	return xor_tweak_pre(req) ?:
247 		crypto_skcipher_encrypt(subreq) ?:
248 		xor_tweak_post(req);
249 }
250 
251 static int decrypt(struct skcipher_request *req)
252 {
253 	struct rctx *rctx = skcipher_request_ctx(req);
254 	struct skcipher_request *subreq = &rctx->subreq;
255 
256 	init_crypt(req);
257 	return xor_tweak_pre(req) ?:
258 		crypto_skcipher_decrypt(subreq) ?:
259 		xor_tweak_post(req);
260 }
261 
262 static int init_tfm(struct crypto_skcipher *tfm)
263 {
264 	struct skcipher_instance *inst = skcipher_alg_instance(tfm);
265 	struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
266 	struct priv *ctx = crypto_skcipher_ctx(tfm);
267 	struct crypto_skcipher *cipher;
268 
269 	cipher = crypto_spawn_skcipher(spawn);
270 	if (IS_ERR(cipher))
271 		return PTR_ERR(cipher);
272 
273 	ctx->child = cipher;
274 
275 	crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
276 					 sizeof(struct rctx));
277 
278 	return 0;
279 }
280 
281 static void exit_tfm(struct crypto_skcipher *tfm)
282 {
283 	struct priv *ctx = crypto_skcipher_ctx(tfm);
284 
285 	if (ctx->table)
286 		gf128mul_free_64k(ctx->table);
287 	crypto_free_skcipher(ctx->child);
288 }
289 
290 static void free_inst(struct skcipher_instance *inst)
291 {
292 	crypto_drop_skcipher(skcipher_instance_ctx(inst));
293 	kfree(inst);
294 }
295 
296 static int create(struct crypto_template *tmpl, struct rtattr **tb)
297 {
298 	struct crypto_skcipher_spawn *spawn;
299 	struct skcipher_instance *inst;
300 	struct crypto_attr_type *algt;
301 	struct skcipher_alg *alg;
302 	const char *cipher_name;
303 	char ecb_name[CRYPTO_MAX_ALG_NAME];
304 	u32 mask;
305 	int err;
306 
307 	algt = crypto_get_attr_type(tb);
308 	if (IS_ERR(algt))
309 		return PTR_ERR(algt);
310 
311 	if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
312 		return -EINVAL;
313 
314 	mask = crypto_requires_sync(algt->type, algt->mask);
315 
316 	cipher_name = crypto_attr_alg_name(tb[1]);
317 	if (IS_ERR(cipher_name))
318 		return PTR_ERR(cipher_name);
319 
320 	inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
321 	if (!inst)
322 		return -ENOMEM;
323 
324 	spawn = skcipher_instance_ctx(inst);
325 
326 	err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
327 				   cipher_name, 0, mask);
328 	if (err == -ENOENT) {
329 		err = -ENAMETOOLONG;
330 		if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
331 			     cipher_name) >= CRYPTO_MAX_ALG_NAME)
332 			goto err_free_inst;
333 
334 		err = crypto_grab_skcipher(spawn,
335 					   skcipher_crypto_instance(inst),
336 					   ecb_name, 0, mask);
337 	}
338 
339 	if (err)
340 		goto err_free_inst;
341 
342 	alg = crypto_skcipher_spawn_alg(spawn);
343 
344 	err = -EINVAL;
345 	if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
346 		goto err_free_inst;
347 
348 	if (crypto_skcipher_alg_ivsize(alg))
349 		goto err_free_inst;
350 
351 	err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
352 				  &alg->base);
353 	if (err)
354 		goto err_free_inst;
355 
356 	err = -EINVAL;
357 	cipher_name = alg->base.cra_name;
358 
359 	/* Alas we screwed up the naming so we have to mangle the
360 	 * cipher name.
361 	 */
362 	if (!strncmp(cipher_name, "ecb(", 4)) {
363 		unsigned len;
364 
365 		len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
366 		if (len < 2 || len >= sizeof(ecb_name))
367 			goto err_free_inst;
368 
369 		if (ecb_name[len - 1] != ')')
370 			goto err_free_inst;
371 
372 		ecb_name[len - 1] = 0;
373 
374 		if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
375 			     "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
376 			err = -ENAMETOOLONG;
377 			goto err_free_inst;
378 		}
379 	} else
380 		goto err_free_inst;
381 
382 	inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
383 	inst->alg.base.cra_priority = alg->base.cra_priority;
384 	inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
385 	inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
386 				       (__alignof__(be128) - 1);
387 
388 	inst->alg.ivsize = LRW_BLOCK_SIZE;
389 	inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
390 				LRW_BLOCK_SIZE;
391 	inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
392 				LRW_BLOCK_SIZE;
393 
394 	inst->alg.base.cra_ctxsize = sizeof(struct priv);
395 
396 	inst->alg.init = init_tfm;
397 	inst->alg.exit = exit_tfm;
398 
399 	inst->alg.setkey = setkey;
400 	inst->alg.encrypt = encrypt;
401 	inst->alg.decrypt = decrypt;
402 
403 	inst->free = free_inst;
404 
405 	err = skcipher_register_instance(tmpl, inst);
406 	if (err) {
407 err_free_inst:
408 		free_inst(inst);
409 	}
410 	return err;
411 }
412 
413 static struct crypto_template crypto_tmpl = {
414 	.name = "lrw",
415 	.create = create,
416 	.module = THIS_MODULE,
417 };
418 
419 static int __init crypto_module_init(void)
420 {
421 	return crypto_register_template(&crypto_tmpl);
422 }
423 
424 static void __exit crypto_module_exit(void)
425 {
426 	crypto_unregister_template(&crypto_tmpl);
427 }
428 
429 subsys_initcall(crypto_module_init);
430 module_exit(crypto_module_exit);
431 
432 MODULE_LICENSE("GPL");
433 MODULE_DESCRIPTION("LRW block cipher mode");
434 MODULE_ALIAS_CRYPTO("lrw");
435